A west metro lake will be the second in the country and the first in the state to be a testing ground for a new solution in the fight against zebra mussels in Minnesota.

The U.S. Environmental Protection Agency has approved the use of potassium chloride, or liquid potash, on Christmas Lake near Lake Minnetonka to kill off zebra mussels found near the boat launch this summer. The state Department of Natural Resources now plans to use it in the frozen lake this month once the state Agriculture Department approves potash as a registered use.

“It gives us a higher level of hope that we will in fact eradicate zebra mussels from Christmas Lake,” said Joe Shneider, a resident and president of the lake’s homeowners’ association. “There’s no sure thing, but this is the best we collectively know how to do.”

The DNR put in the emergency exemption request for potash, which has been used successfully in two other states, Texas and Virginia. Last week, about two weeks later, the EPA gave its approval. Now, Minnesota could have the second lake in the country to use potash to kill off zebra mussels — and the first frozen one.

Keegan Lund, a DNR invasive species specialist, said it will be the first above-ice application of potash. Crews plan to drill a few holes in the ice and use hoses to treat the lake with the pesticide.

It’s part of the intensifying efforts in Minnesota to slow the spread of the fingernail-sized mussel, which can quickly proliferate by the millions and has infested hundreds of waterways statewide. While efforts have been largely focused on prevention and education, local and state leaders are now going on the offensive with potash and Zequanox, a biological pesticide that Christmas Lake was the first in the country to use last fall.

While officials later said the treatment, which cost about $9,300, worked in the closed-off 50-by-60-foot area, they discovered more zebra mussels outside that area. Water temperature was too low to use Zequanox, so the DNR, along with the Minnehaha Creek Watershed District, applied for federal and state approval for potash, which has killed off zebra mussels in waterways in Texas and Virginia as well as Lake Winnipeg in Canada.

Last month, U.S. Rep. Erik Paulsen sent a letter to the EPA encouraging its quick approval of the use of potash.

Now, the EPA’s approval includes both Christmas Lake and Lake Independence near Maple Plain. But because a barrier blocking off zebra mussels in Lake Independence was removed, Lund said potash may not be able to be used until next spring.

If it works, like Zequanox, the pesticide isn’t likely to be a solution for every Minnesota lake and river. Officials say the treatments are too difficult and costly to kill off zebra mussels on larger lakes and ones that are fully infested.

“Every new infestation is different,” Lund said, “and the response is different.”